【作者】 厉宝增；

【导师】 明海； 谢建平；

【作者基本信息】 中国科学技术大学 ， 光学， 2007， 博士

【摘要】 本论文工作以美国波士顿应用科技公司与本实验室的合作项目为依托，着重研究了稀土掺杂PLZT的荧光和上转换发光的光学特性，并成功地用PLZT可变光衰减器在低工作电压下对光纤激光器实现了调Q的脉冲输出。本论文工作为掺杂PLZT研发各种高性能光器件提供了物理基础。论文主要成果有：1．对掺钕PLZT的辐射特性进行了研究。由掺钕PLZT的吸收光谱计算得到J-O强度参量，用强度参量结合其荧光光谱和1066nm处的荧光衰减谱，计算了⁴F_3／2→⁴I_J^／的自发辐射跃迁几率、辐射寿命、量子效率以及受激发射截面。这些光学参数表明掺钕PLZT最有可能制成的是1066nm波长的激光器和光放大器。2．详细研究了不同Tm³⁺掺杂浓度PLZT的光谱特性。从发光强度、辐射寿命、荧光有效线宽等几个方面综合分析，认为7％Tm³⁺掺杂浓度的PLZT比较合适于有源光器件的研发；初步研究了Ho³⁺／Tm³⁺双掺PLZT在2μm波段（⁵I₇→⁵I₈）的发光，探讨了Tm³⁺对Ho³⁺的敏化机制。采用玻尔兹曼分布比较了不同Ho³⁺浓度下，Tm³⁺到Ho³⁺的能量转移效率的变化。3．研究得到了Er掺杂、Er／YbX^掺以及Nd掺杂PLZT上转换发光的一些规律。掺Er和Er／Yb双掺的PLZT是一种上转换效率较高的发光材料。在980nm光的激发下，能有效发射可见光。如果进一步增大并调整Er³⁺，Yb³⁺的掺杂浓度，同时因PLZT陶瓷较高的电光系数，该材料有望制成电光调O的双功能上转换激光器。三种掺杂条件下的发光强度与抽运强度的对数关系曲线都表明该材料的可见发射光为双光子过程。又比较了Er／Yb双掺PLZT在室温下和加热条件下上转换发光强度的变化，从发光机制上，分析了各个峰随温度变化不同的原因。我们还成功观测到了1％Nd掺杂PLZT在807nm光激发下的上转换荧光光谱，分析了上转换过程中的激发态吸收和能量传递过程。4．首先研究了PLZT可变光衰减器（VOA）的特性。将它作为掺Er光纤激光器的调Q开关，在无直流偏置、工作电压仅为255V的条件下，于1546nm处成功地获得了稳定的调Q脉冲输出。本文创新点和特色：1．在Judd-Ofelt理论基础上，由掺钕PLZT的吸收光谱求得Nd³⁺在PLZT中的J-O强度参量Ωi，并结合测量出的荧光光谱和1066nm处的荧光衰减谱，计算了⁴F_3／2→⁴I_J^／的自发辐射跃迁几率、辐射寿命、量子效率以及受激发射截面。2．详细地研究了不同Tm³⁺掺杂浓度PLZT的光谱特性。J-O强度参量的结果表明即使7％的Tm³⁺掺杂浓度仍未使PLZT晶格发生扭曲。综合实验和理论分析得出的结论是，PLZT在7％的Tm³⁺掺杂浓度下比较合适于1.8μm波段有源光器件的研发。3．首次报道了Er掺杂、Er／Yb双掺PLZT较强的上转换发光，证实了该材料的可见发射光为双光子过程。成功观测到了Nd掺杂PLZT在807nm光激发下的上转换荧光光谱，并分析了其上转换过程中的激发态吸收和能量传递过程。4．运用PLZT可变光衰减器作为掺Er光纤激光器的调Q开关，在无直流偏置、工作电压仅为255V的条件下，于1546nm处成功地实现了稳定的调Q脉冲输出。与LiNbO₃和KDP等常用调Q晶体的工作电压为千伏量级相比，PLZT调Q开关带来了使用上的极大方便。更多还原

【Abstract】 The works in this thesis are on the basis of the projects ,which origin from our cooperative item with BATI（ Boston Applied Technologies, Incorporated）. The content of projects include that study on optical characteristics, radiative properties of rare earth doped PLZT and provide a physical supply for devolopment of new optical devices. For these goals, the optical properties, radiative properties of rare earth doped PLZT and PLZT’s application on Q-switch will be studied in this thesis.1. Based on Judd-Ofelt（J-O）theory, the J-O intensity parameters were calculated using the emission spectrum of Nd doped PLZT. The J-O intensity parameters have been used to calculate the radiative transition probabilities of the ⁴F_3/2→⁴I_J, transition, the radiative lifetime of ⁴F_3/2 level and the stimulated emission cross-section of the ⁴F_3/2→⁴I_J, transition.The fluorescence lifetime of the ⁴F_3/2 was measured.2. Optical properties of defferent Tm3+ concentration doped PLZT have been discussed in detail. Three sets of Judd-Ofelt parameters show that the ion concentration of 7% does not infect host environment . From the results of experiments and theory analysis, We can conclude that 7% doped concentration is sutible for development of active photonic devices at the waveband of 1.8μm.3. We fist report that unde 980nm laser excitation, visible up-converted luminescence spectra of Er and Er/Yb in PLZT have been observed . Lasers power dependence on upconverted emissions revealed that two-photon process lead to green or red emissions. Green light from upconversion of Nd in PLZT is also observed. Its two upconversion mechanisms: exiced state absorption and energy transfer is discussed specificly.4. We apply Variable Optical Attenuater（VOA） as Q-switch of Er doped fiber laser.1560nm Q- pulse laser is obtained under no bias voltage ,but working voltage is only 255 V, which is much smaller than that of LiNbO3 or KDP.The innovation points and high lights of this thesis include:1 .Based on Judd-Ofelt（J-O）theory, the J-O intensity parameters are calculated using the emission spectrum of Nd³⁺ doped PLZT. The intensity parameters have been used to evaluate the various radiative parameters, such as induced-emission cross section , lifetime of metastable state and quantum efficiency, for the Nd3+ ions doped PLZT.2. Through the research on optical characteristics of different Tm³⁺ concentration doped PLZT, three sets of J-0 intensity parameters show that enven if doping content of 7% Tm³⁺ , PLZT’lattice is not yet distorted. In the waveband of 1.8μm , fluorescence intensity of 7% doping content is much stronger than that of 3% and 1%. Though the radiative lifetime of 7% is a little shorter than that of 3% and 1%, it is comparable to those of commercial Tm³⁺ doped laser glasses. Combining the theoretical analysis and experimental results ,we hold that Tm doped PLZT with 7% doping concentration is more suitable for development of optical devices at the waveband of 1.8μm.3. We have acquired some rules about upconversion luminescence of Er, Er/Yb, Nd doped PLZT. We find that Er/Yb doped PLZT is a very efficient material for upconversion. It may be acted as a probable material for upconversion laser at the same time it has a high e-o coefficient. In three ions doped conditions, the relationship between luminescence power and pump power all verify that the visible upconversion process is two-photon emission mechanism. We also successfully observed upconversion luminescence of Nd doped PLZT at the pump of 807nm.4. First we research some characteristics of VOA based on PLZT. Then we use it as an E-0 Q-switch of Er doped fiber laser. Under the condition of work voltage at 255V, We successfully get a steady-going Q-swith pulse.更多还原